Smart load pin for draw-works

ABSTRACT

A smart load pin may be configured to measure a load on a hook of a draw-works system. The smart load pin may also include circuitry to convert the measured load to a digital value representative of the measured load, wherein the digital value represents the value of the measured load in engineering units and to transfer the digital value representative of the measured load to a control system located at a derrick. The data from the smart load pin may be used in adjusting, with a control system, operation of the draw-works system based, at least in part, on the received digital value representative of the measured load.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims priority to and is a continuation of U.S. patentapplication Ser. No.: 15/051,333, filed Jun. 8, 2017, entitled “SmartLoad Pin for Draw-Works,” which claims priority to U.S. ProvisionalPatent Application No.: 62/119,397, filed Feb. 23, 2015, entitled“Intelligent Load Pin for Draw-works,” each of which is incorporatedherein by reference.

FIELD OF THE DISCLOSURE

This disclosure relates to equipment used for drilling operations in oiland gas wells. More specifically, this disclosure relates to a methodfor measuring the load on the hook of a draw-works in an intelligentmanner.

BACKGROUND

Conventional methods of measuring and reporting hookload has not changedsignificantly since 1926. One significant change in this field was theshift from using a diaphragm-type weight indicator to a strain cellintegrated with the load bearing pins. There have been some incrementalimprovements over time, but no significant changes since that time. Oneproblem with the conventional strain measurements is the longcommunication path of the strain measurement before conversion toengineering units. Each component in the path creates a new source fornoise and a new possible entry point for error until the data is inengineering units. FIG. 1 is a block diagram illustrating conventionalpaths and processing steps for the hookload signal from the measurementto the control system according to the prior art. In particular, FIG. 1illustrates two processing paths 140 and 150. Both of the paths 140 and150 include similar equipment (sensor 122, converter 124, barrier 126,barrier 128, converter 130, scaler 132, and controller 134) arrangeddifferently in a pin 110, derrick cabinet(s) 112, and control cabinet114. Each of the equipment is arranged to convert the measured straininto a final engineering unit measurement (such as kips).

FIG. 1 illustrates different process flow of the signal for the hookloadmeasurement derived from transducer to HMI display. The strain gauge inthe pin outputs a millivolt signal that is accepted in to anintrinsically safe barrier. The barrier then converts this millivoltsignal to a milliamp signal, then drives the signal from the fieldstation (e.g., junction box) to a control cabinet. Inside the controlcabinet, a control system will either accept the current signal or, insome cases, present this signal to another intrinsically safe barrierthat converts the signal into a 0 to 10 Volt signal, terminated into ananalog input on the control system I/O device. This signal nowrepresents the minimum and maximum output of the original strain gage.The PLC is given instruction to place a “real world” value to measureload commonly represented in Tons or kips. An analog/digital (A/D)converter in the PLC assigns a value to present data to the user basedon an formula, which takes a known min and max value and creates a slopebased on the difference between the delta. In short, a real world valueis displayed to the user based on the amount of force applied to straingauge.

Conventional hook load measurement is currently derived from a fewdifferent methods, including: load cells installed in pins connectingthe topdrive to the travelling block, load cells installed in pins onthe crown block, load cells installed in the deadline, and Strainmeasurement sensors installed on the Steel Wire Rope (SWR). The firstthree methods involve property of the drilling contractor, whereas thefourth is installed by a third party mud logging service provider. Theattractiveness to the fourth type of installation is that it does notdepend on any rig-based instrumentation and can easily be installedwithout taking the block out of service. The downside is it issusceptible to breakage, dampening, and its accuracy is debatable.

The third method, in which the load measurement is from the deadline,has been a conventional method consisting of a stepdown piston andhydraulic hose connected directly to a mechanical gauge or to a pressuresensor that will convert to an electrical signal to be display. Thestrengths to this method include simplicity, ease of access and issimple to troubleshoot. The downsides are inherent dampening, lag, andoverall accuracy concerns in the measurement as it is located very faraway from the measurement point. Variations in WOB and HL can directlyinfluence the control process as well as the drilling process.

The second method is an improvement on the third by placing themeasurement location much closer to what is intended to be measured andremoves the problems of a hydraulic circuit and pressure transducer byusing a strain gauge sensor. One or more strain gauge sensors arelocated in each load bearing clevis pin required to lock the crown blockin to its position. One conventional installation includes four loadpins providing four load measurements. For an accurate measurement in amarine environment all four sensors need to be operational as the loaddistribution across the four pins is not expected to be homogenous.

During the manufacturing process, the strain gauge load cell is exposedto a full range of its intended loads on a hydraulic press. Also,incorporated into this press is a calibration load cell that istraceable back to NIST (National Institute of Standards and Technology).A calibration certification would accompany a load cell with two or more(typically around ten) calibration value pairs. As the strain gauge loadcell does not natively output mA (current loop), a specialized signalconditioner (e.g. KFD2-WAC-Vx1d) is required. The strain measurement isaccomplished by supplying an excitation voltage across two points on theWheatstone bridge and then measuring the resultant voltage on the otherside. The signal native to the strain cell is proportional to theexcitation voltage and that variation of the measurement section'sresistance. The signal units as a result are mV/V. The signal in thisform cannot be used directly by a control system. The signal conditionermentioned converts the mV/V measurement to a current loop signal (4-20mA). This resultant signal can be used by the control system, however inorder to use this signal and the factory calibration the strain gaugecell and the signal conditioner must always be connected and paired withthe specific load cell in the circuit. The signal conditioner has ‘zero’and ‘span’ adjustments (potentiometers or digitally configured), ifthese are adjusted in the field or a different conditioner is used itinvalidates the factory calibration.

A deficiency sometimes seen in the industry during the installationprocess is that once the load cells are installed in the field, anothereffort of deriving the same coefficients is done but with roughlyestimated loads. To accomplish this in-field calibration the fieldengineer would request the rig crew to apply the maximum load aspossible to the hook. The load applied is approximate (unless areference cell is available on board), normally the full range of theload cell cannot be fully realized offshore unless it is duringoperations. The issues with this method are: the reference load usedwill not be calibrated to a NIST or known standard; the load applied isnot through the entire range; operation requires recalibration ofdraw-works when replacing a load cell or barrier; and the measurementsare subject to field errors.

The obvious answer to the above problems is to use the originalcalibration. It is not clear why this is currently not always done. Itcan be speculated that it was used at one time, but if the measured andactual loads did not match the simplest solution in the field would havebeen to adjust the measurements to align with the test load on board therig. This would then require an in-field ‘re-calibration’ to be done. Asmentioned above there are also load cells that are installed at thedeadline. These load cells will be less accurate as they are fartheraway from the measurement point. If both the load pin and the deadlineload cell are installed, to ensure the measurements can corroborate oneanother the friction losses in the system need to be accounted for. Asimple model we typically used to estimate some of these loses is shownin the following equation:

$\frac{\left\lbrack {\left( e_{t - {mech}}^{N_{l}} \right) - 1} \right\rbrack}{\left\lbrack {\left( e_{t - {mech}}^{N_{l}} \right){N_{l}\left( {e_{t - {mech}} - 1} \right)}} \right\rbrack}e_{{rev}\_ {mech}}$

where e_(t-meth)=Tackle Efficiency=1.015; N₁=number of lines;F_(hl)=Hookload observed; F_(fs)=load on the fast line, where

F_(hl)=F_(fs)N₁e_(rev-mech)

The calculation above only addresses tackle efficiency, there will beother friction losses that will need to be accounted for. In 2012Hookload was defined by U.MME with NTNU as “The sum of verticalcomponents of the forces acting on the drillstring attached to thehook.” There is expected to be other friction losses, even for thebecket pin style load cell installation. It is expected that they arerelatively small, but those losses should be quantified. The importanceof the hookload measurement in the control system is that it executesconfigured responses based on certain deviations of hookload duringvarious operations. If the hookload values are not reliable this poses achallenge to the user as the system may not respond in a predictablemanner.

First, it is important to recognize that some system suppliers havetermed the infield rescaling of the load measurement a calibration,despite it is in fact not a calibration. An infield re-scaling is notsufficient and as a result is introducing unnecessary error into theload measurement. It can be argued that this error is sufficientlysignificant such that it has contributed to the necessity forrecalibrations of multiple installations in the past. During factorytesting these load cells pass through a series of tests. The pin is putthrough its usable range and the manufacturer generates a table whichmaps the electrical signals from the pin's strain measurement circuit toa real work load. This mapping is accomplished with a degree of accuracyby using a NIST traceable load cell.

Conventionally, there can be two or more “calibrations” performed forthe draw-works load cells. The first calibration occurs at the factorywhere a load cell is exposed to the range of forces. The measurement ofthese forces is done with a NIST (National Institute of Standards andTechnology) traceable load cell that permanently resides at the factory.For a specific pin and the electrical signal, these forces are capturedduring the factory calibration process and provided as a table with theload cell's certificates. The second calibration that occurs once theload cell is installed on board the vessel is a field calibration usinga field procedure. To summarize the procedure, it attempts to expose theload cell as fitted in the draw-works with estimated loads as opposed toknown loads (e.g. NIST). Another drawback is the load cell is notexposed to its entire range, but only a faction. The loads experiencedby the crown or travelling block pins will not be equal across all loadcells. This is due to the load distribution the sheaves and asymmetricfriction losses from the mechanical coupling. This inequality may havecause contention with the original design and it was established toinstitute a field calibration.

SUMMARY

Measuring the load at the traveling block can produce accurate results.The manner of the conversion from a millivolts (mV) signal produced bythe sensor to engineering units for processing directly influences thisaccuracy. A system can be adapted for use with load pins, includingconventional load pins, that provides improved conversion processes andincreased accuracy. Such a system may include a “smart load pin.”

The smart load pin may include one or more features, including:intelligent self-diagnostics, such that control software is able todetect a failure; having less external components required for it tooperate; not requiring constant recalibration, such as by performingfactory calibration in controlled conditions to a known standard;minimizing the hysteresis concavity error, which improves at least 1%accuracy full scale in hookload without introducing excessivecomplexity; including additional sensors integrated in the pin, such asaccelerometers and rate gyros to provide more motion data about the pinand the topdrive itself; applying temperature compensation tomeasurements beyond that of the foil strain gauge design; communicatingthis information over a field bus protocol to facilitate reporting theloads in engineering units with all the compensations applied; improvingthe integrity of the data through error checking in the field busprotocol; removing the requirement to update the control system codewhen replacing the load pin; leveraging the same wiring (service loop)as currently in place; providing field bus communications that can beused either in place of or in addition to a robust wirelesscommunication technology from the load cell as well; and/or using thesame load pin housing design as in use today, by allowing additionalelectronics to be fitted in the existing cavity of the load cell orinstalled or installed immediately outside and adjacent to the loadcell.

According to one embodiment, a method for controlling a draw-workssystem may include measuring, with a load pin, a load on a hook of adraw-works system; converting, with the load pin, the measured load to adigital value representative of the measured load, wherein the digitalvalue represents the value of the measured load in engineering units;transferring, from the load pin, the digital value representative of themeasured load to a control system located at a derrick; and/oradjusting, with the control system, operation of the draw-works systembased, at least in part, on the received digital value representative ofthe measured load.

The foregoing has outlined rather broadly certain features and technicaladvantages of embodiments of the present invention in order that thedetailed description that follows may be better understood. Additionalfeatures and advantages will be described hereinafter that form thesubject of the claims of the invention. It should be appreciated bythose having ordinary skill in the art that the conception and specificembodiment disclosed may be readily utilized as a basis for modifying ordesigning other structures for carrying out the same or similarpurposes. It should also be realized by those having ordinary skill inthe art that such equivalent constructions do not depart from the spiritand scope of the invention as set forth in the appended claims.Additional features will be better understood from the followingdescription when considered in connection with the accompanying figures.It is to be expressly understood, however, that each of the figures isprovided for the purpose of illustration and description only and is notintended to limit the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the disclosed system and methods,reference is now made to the following descriptions taken in conjunctionwith the accompanying drawings.

FIG. 1 is a block diagram illustrating conventional paths and processingsteps for the hookload signal from the measurement to the control systemaccording to the prior art.

FIG. 2 is a block diagram illustrating a processing path and steps fortransmitting, from a smart load pin, the hookload signal from themeasurement to the control system according to one embodiment of thedisclosure.

FIGS. 3A and 3B are a three-dimensional rendering of a becket pin loadcell with smart instrumentation, including squares representing strainsensors showing an approximate but not limiting position, according toone embodiment of the disclosure.

FIG. 4 is a circuit diagram illustrating an electrical layout for signalprocessing involving measurements from the load pin according to oneembodiment of the disclosure.

FIG. 5 is a block diagram illustrating primary interfaces for aprocessor to interface with strain measurement devices according to oneembodiment of the disclosure.

FIG. 6 is a flow chart illustrating a method of controlling adrill-works system with input from a smart load pin according to oneembodiment of the disclosure.

DETAILED DESCRIPTION

The smart pin relieves the control system of interpreting the hook loadby sending a pre-scaled, pre-calibrated load signal via digital data(such as over a field bus). This signal now becomes a “pass-through”value and can use standard conversion methods to display the hookload.In addition to strain measurements, additional instrumentation isinstalled in the load pin and multiplexed on the communications protocolwith the strain measurements. One example is the inclusion of aninertial measurement unit (IMU). There are many applications of IMUs inspatial measurement of block motion, but from the perspective of thestrain sensing this would help further identify and model asymmetricalloading across pairs of load pins. If the reported pin loads are notreasonably equivalent, this could be attributed to asymmetrical loadingof the equipment on the pins. One of the causes of this could be as aresult of misalignment of the travelling equipment.

FIG. 2 illustrates an example of an internally instrumented load pin fordrilling applications. FIG. 2 is a block diagram illustrating aprocessing path and steps for transmitting, from a smart load pin, thehookload signal from the measurement to the control system according toone embodiment of the disclosure. A load pin 210 may include a strainsensor 212, an operational amplifier 214, an analog-to-digital converter(ADC) 216, and a scaling and offset conversion block 218. The load pin210 is shown in more detail in FIGS. 3A and 3B. FIGS. 3A and 3B are athree-dimensional rendering of a becket pin load cell with smartinstrumentation, including squares representing strain sensors showingan approximate but not limiting position, according to one embodiment ofthe disclosure. Referring back to FIG. 2, strain may be converted by thesensor 212 into a millivolts signal and processed in the load pin 210 toa signal corresponding to engineering units (such as kips). Thatengineering units signal may be processed in a barrier 222 of derrickcabinet(s) 220, and barrier 232 and controller 234 of control cabinet230. In other embodiments, the amplifier 214, ADC 216, and scaling andoffset conversion block 218 may be implemented in a processor forexecuting code configured to perform steps that accomplish similar tasksas the operational amplifier 214, the analog-to-digital converter (ADC)216, and the scaling and offset conversion block 218.

One circuit design for such a smart pin as the pin 210 of FIG. 2 isillustrated in FIG. 4. A voltage regulator 404 may be used to provide astable voltage for source power for integrated circuits (ICs) onboardthe smart pin. Op-amps 408A-D (instrumentation operational amplifier)may be applied to the mV/V signal for amplification of the signalreceived from Wheatstone bridges 406A-D, and a reference voltage may bemeasured as well. A thermocouple 414 may monitor a temperature of thesmart load pin and provide the processor (such as a controller) 412 withthe ability to compensate for these thermal variations. An inertialmotion unit (IMU) 416 may provide multiple degrees of freedom for posemeasurement. A fieldbus communication interface 418 may be used by theprocessor 412 to transfer data to the control system or directly to aninstrumentation device/network.

One location for a smart load pin is on a cable within a service loophaving the least impact on our signal. Further, the load pin may includevarious shielding and insulation based on the environment. In addition,various baud rates may be used in transmitting data packets to findsufficient accuracy. Further, forward error correction or channel codingmay be applied to data to control errors in data transmission.

In one embodiment, the processor 412 may be an MCU. Many of the criticalmeasurements provided to the MCU 412 may pass through a dedicated ADC,although alternatively an integrated ADC for auxiliary measurements maybe included. In one embodiment, the dimensions of the board for the MCUmay be smaller that approximately 19 mm and be capable of operating in atemperature range of −40 C→100 C. Further, communication to the MCU 412may use I2C and/or SPI protocols, and a debugging port such as JTAG maybe included.

FIG. 5 is a block diagram illustrating interfaces for a processor tointerface with strain measurement devices according to one embodiment ofthe disclosure. A processor 502 may receive data from one or more straingauge circuits, which may be integrated in smart load pins. Theprocessor 502 may also receive data from an IMU or other components overan 12C interface, including data such as Vx, Vy, Vz, Wx, Wy, and Wzvector values. The processor 502 may compute values to output to a UARTlevel-shifted output serial data for testing or further processing withanother processor or controller and to output SPI-output for integrationwith a Profichip. Further, the processor 502 may include an interfacefor transmitting debug information and receiving new flash programming,such as over a USB bus.

FIG. 6 is a flow chart illustrating a method of controlling adrill-works system with input from a smart load pin according to oneembodiment of the disclosure. A method 600 begins at block 602 withmeasuring, with a load pin, a load on a hook of a draw-works system.Then, at block 604, the method 600 continues with converting, with theload pin, the measured load to a digital value representative of themeasured load, wherein the digital value represents the value of themeasured load in engineering units. Next, at block 606, the method 600continues with transferring, from the load pin, the digital valuerepresentative of the measured load to a control system located at aderrick. Then, at block 608, the method 600 may further includeadjusting, with the control system, operation of the draw-works systembased, at least in part, on the received digital value representative ofthe measured load

The schematic flow chart diagram of FIG. 2 and FIG. 6 is generally setforth as a logical flow chart diagram. As such, the depicted order andlabeled steps are indicative of aspects of the disclosed method. Othersteps and methods may be conceived that are equivalent in function,logic, or effect to one or more steps, or portions thereof, of theillustrated method. Additionally, the format and symbols employed areprovided to explain the logical steps of the method and are understoodnot to limit the scope of the method. Although various arrow types andline types may be employed in the flow chart diagram, they areunderstood not to limit the scope of the corresponding method. Indeed,some arrows or other connectors may be used to indicate only the logicalflow of the method. For instance, an arrow may indicate a waiting ormonitoring period of unspecified duration between enumerated steps ofthe depicted method. Additionally, the order in which a particularmethod occurs may or may not strictly adhere to the order of thecorresponding steps shown.

If implemented in firmware and/or software, functions described abovemay be stored as one or more instructions or code on a computer-readablemedium. Examples include non-transitory computer-readable media encodedwith a data structure and computer-readable media encoded with acomputer program. Computer-readable media includes physical computerstorage media. A storage medium may be any available medium that can beaccessed by a computer. By way of example, and not limitation, suchcomputer-readable media can comprise random access memory (RAM),read-only memory (ROM), electrically-erasable programmable read-onlymemory (EEPROM), compact disc read-only memory (CD-ROM) or other opticaldisk storage, magnetic disk storage or other magnetic storage devices,or any other medium that can be used to store desired program code inthe form of instructions or data structures and that can be accessed bya computer. Disk and disc includes compact discs (CD), laser discs,optical discs, digital versatile discs (DVD), floppy disks and Blu-raydiscs. Generally, disks reproduce data magnetically, and discs reproducedata optically. Combinations of the above should also be included withinthe scope of computer-readable media.

In addition to storage on computer readable medium, instructions and/ordata may be provided as signals on transmission media included in acommunication apparatus. For example, a communication apparatus mayinclude a transceiver having signals indicative of instructions anddata. The instructions and data are configured to cause one or moreprocessors to implement the functions outlined in the claims.

Although the present disclosure and certain representative advantageshave been described in detail, it should be understood that variouschanges, substitutions and alterations can be made herein withoutdeparting from the spirit and scope of the disclosure as defined by theappended claims. Moreover, the scope of the present application is notintended to be limited to the particular embodiments of the process,machine, manufacture, composition of matter, means, methods and stepsdescribed in the specification. As one of ordinary skill in the art willreadily appreciate from the present disclosure, processes, machines,manufacture, compositions of matter, means, methods, or steps, presentlyexisting or later to be developed that perform substantially the samefunction or achieve substantially the same result as the correspondingembodiments described herein may be utilized. Accordingly, the appendedclaims are intended to include within their scope such processes,machines, manufacture, compositions of matter, means, methods, or steps.

What is claimed is:
 1. A method for controlling a draw-works system,comprising: measuring, with a load pin, a load on a hook of a draw-workssystem; converting, with the load pin, the measured load to a digitalvalue representative of the measured load, wherein the digital valuerepresents the value of the measured load, the converting including:converting, with a gauge of the load pin, the measure load to an analogrepresentation of the measured load, converting, with ananalog-to-digital converter of the load pin, the analog representationto a digital value, and compensating, with an MCU of the load pin, thedigital value to account for variations in the measuring of the load;and transferring the digital value from the load pin to a control systemlocated at a derrick.
 2. The method of claim 1, further comprisingadjusting, with the control system, operation of the draw-works systembased, at least in part, on the digital value.
 3. The method of claim 1,wherein the gauge is a transducer strain gauge.
 4. The method of claim1, wherein the measured load is represented as a tension value.
 5. Themethod of claim 1, wherein the load pin is coupled to at least one of atraveling block, a drilling hook, or a top drive of the draw-workssystem.
 6. The method of claim 1, wherein transferring includestransferring the digital value via at least one of a physicalcommunications bus or a wireless communication system.
 7. A load pin,comprising: a sensor configured to measure a load on a hook of adraw-works system; and electronic circuitry coupled to the sensor andconfigured to: convert a measured load generated by the sensor to ananalog representation of the measured load, convert the analogrepresentation to a digital value, compensate the digital value toaccount for variations in the measured load to produce a compensateddigital value, and transfer the compensated digital value to a controlsystem located at a derrick.
 8. The load pin of claim 7, wherein theelectronic circuitry further comprises: an operational amplifier coupledto the sensor; and an analog-to-digital converter (ADC) coupled to theoperational amplifier.
 9. The load pin of claim 8, wherein theelectronic circuitry is further configured to scale and offsetconversion of an output of the analog-to-digital converter (ADC). 10.The load pin of claim 7, wherein the load pin is configured to becoupled to at least one of a traveling block, a drilling hook, and a topdrive of the draw-works system.
 11. The load pin of claim 7, wherein thetransferring includes transferring the digital value via at least one ofa physical communications bus or a wireless communication system
 12. Anon-transitory processor-readable medium storing code representinginstructions to be executed by a processor, the code comprising code tocause the processor to: receive data associated with a measured load ona hook of a draw-works system; convert the measured load to an analogvalue representative of the measured load; convert the analog value to adigital value; transfer the digital value to a control system that islocated at a derrick.
 13. The non-transitory processor-readable mediumof claim 12, wherein the measured load is represented as a tensionvalue.
 14. The non-transitory processor-readable medium of claim 13,wherein the tension value is measured from at least one of a travelingblock, a drilling hook, or a top drive of the draw-works system.
 15. Thenon-transitory processor-readable medium of claim 12, wherein code tocause the processor to transfer includes code to cause the processor totransfer the digital value via at least one of a physical communicationsbus or a wireless communication system.
 16. The non-transitoryprocessor-readable medium of claim 12, wherein the code furthercomprises code to cause the processor to scale and offset conversion ofthe measured load.